The Whole Earth Sings

One of the fun units in physics is the study of vibrations and resonance. A simple demonstration of sympathetic vibration is an apparatus that consists of a tuning fork mounted on a wooden box. If you place near it a second box with a tuning fork of the same frequency, you can hear the effect called “resonance” or “sympathetic vibration.” Striking the tuning fork on one box will cause the tuning fork on the second box to start “singing” without being touched. A second tuning fork with a different vibration frequency will not respond. The amazing thing is that the whole earth sings.

When building a guitar or violin, a craftsman has to be very careful not to allow any part of the instrument’s box to naturally vibrate at the same frequency as the strings. If it does, that frequency will be louder than all other frequencies, and the sound will be distorted.

This effect is not confined to tuning forks and musical instruments. Resonance is all around us and in us. For example, your inner ear has hairs of varying lengths and thicknesses, resulting in specific vibration frequencies. If a sound at that frequency reaches your ear, the hair will vibrate and signal the brain to identify the pitch. Not having some of those hairs produces tone-deafness.

Taking a fine glass goblet and running a moistened finger around the edge will produce a tone at a specific frequency. That is the natural frequency of the goblet. You can produce a sound at the resonant frequency of a glass that will cause it to shatter, but probably not with any human voice.

Amazingly, researchers have found that everything in the natural world has a resonant frequency. For example, recent research on the Matterhorn near Zermatt, Switzerland, shows that it vibrates with a resonant frequency. The mountain actually vibrates about once every two seconds (.42 cycles per second.). Our ears hear sound frequencies between about 20 and 20,000 cycles per second, so we need instruments to detect the Matterhorn’s frequency.

You could say that the whole earth sings. Interestingly, the Bible refers to mountains, and even stars, singing. (See Isaiah 44:23, 49:13 and Job 38:7). Isaiah and Job certainly didn’t understand their statements to refer to mountain resonance. However, our understanding of what happens in nature gives new meaning to this poetry describing how the whole earth sings praise to God.

— John N. Clayton © 2022

Reference: National Science Foundation research report for January 19, 2022